Improving the Minimum Design Velocity of Sewage Pipes

The minimum design velocity for sewage pipes is set based on the planned quantity; however, deriving a reasonable design with only a single standard is limited. Thus, it is necessary to review whether consistent standards, such as the current minimum flow velocity, can efficiently transport the particles flowing in pipes. Improving the design that can determine the minimum design velocity rate and slope according to the concentration, specific gravity, particle size, and characteristics of the pipe material of the sediment flowing into the sewer system is necessary. In this study, the minimum design velocity for each particle size was examined based on the results of the simulation of fluid-solid multiphase flow required for the review process of hydraulic properties inside the pipe. The minimum design velocity standards for domestic and international sewage systems were investigated and compared, and a minimum design flow rate prediction equation was proposed considering the sedimentation. The equation includes the relationship between the particle size and pipe diameter and can be easily estimated.

Assessing a parallel baffle splitter, an experimental and numerical study on insertion loss and pressure drop

HVAC systems are composed of different noise sources and paths. The non-attenuated propagation of noise through the system has detrimental effects on acoustic comfort of people inside the premises. In order to mitigate the propagated noise, classic parallel baffe splitters are used to reduce the transmitted noise through acoustic coatings. Different methods have been developed to predict the insertion loss of those elements, however, if the input data is not well known these models can lead to deviated results. Additionally, the use of splitters in HVAC systems produces pressure drop which can damage the installed mechanical equipment if that is not well predicted. Currently, the models that estimate pressure drop relate dimensional features and design velocity. However, these models can give overestimated results. In this work an experimental rig was implemented to assess a splitter installed inside of a test duct. Measurements were performed to estimate insertion loss and pressure drop coeffcient, following the guidelines exposed on the ISO 7235 standard. The results were compared with analytical methods. Finally, a numerical method analysis of the test rig was performed, showing the correlation between these results and the experimental data.

Assessing a parallel baffle splitter, an experimental and numerical study on insertion loss and pressure drop

HVAC systems are composed of different noise sources and paths. The non-attenuated propagation of noise through the system has detrimental effects on acoustic comfort of people inside the premises. To mitigate the propagated noise, parallel baffle splitters are used which reduce the transmitted noise through acoustic coatings. Different methods have been developed to predict the insertion loss of those elements, however, if the input data is not well known these models can lead to deviated results. On the other hand, the use of splitter in HVAC systems produces pressure drop which can damage the equipment used if that is not well predicted. Different models are available in the literature, which relates dimensional features and design velocity to estimate the pressure drop coefficient. However, models can give overestimated results. In this work an experimental rig was implemented to assess a splitter installed inside of a test duct. Measurements were performed to estimate insertion loss and pressure drop coefficient, following the guidelines exposed on the ISO 7235 standard. The results were compared with analytic methods. Finally, a numerical method analysis of the test rig was performed, showing the correlation between these results and the experimental data.

Design of the Blade under Low Flow Velocity for Horizontal Axis Tidal Current Turbine

The blade is the key component for energy capture in horizontal axis tidal current turbine, and the blade’s design is directly related to the efficiency of the power generation device. The seawater flow velocity is a crucial parameter for blade design. Since the seawater velocity changes constantly, it is extremely important to determine the design velocity of the blade. This article proposes a calculation method for the design velocity of the blade so that the designed blade can achieve better energy collection efficiency under a variable flow velocity. This study performed the following investigations: (1) The author tested and analyzed the seawater velocity variation at the experimental site, determining the designed flow velocity via calculations; (2) The author combined the blade element momentum and Wilson’s optimization design method using the MATLAB software to calculate the blade shape parameters and predict the performance under a number of different flow velocity forecasts; (3) When testing the device under sea conditions, the experimental results showed that the performance capture devices and digital projections are basically the same, which verifies the validity and effectiveness of the design method.

Experimental and Numerical Study of Collector Geometry Effect on Solar Chimney Performance

There have been many advances in the solar chimney power plant since 1930 and the first pilot work was built in Spain (Manzanares) that produced 50 KW. The solar chimney power plant is considered of a clean power generation that needs to be investigated to enhance the performance by studying the effect of changing the area of passage of air to enhance the velocity towards the chimney to maximize design velocity. In this experimental and numerical study, the reduction area of solar collector was investigated. The reduction area that mean changing the height of glass cover from the absorbing plate (h1=3.8cm, h2=2.6cm and h3=1.28cm). The numerical study was performed using ANSYS Fluent software package (version 14.0) to solve governing equations. The aim of this work was to study the effect of change the height of reduction area to the design velocity (velocity move the blade of turbine at inlet in the chimney). The results showed that the third height (h3=1.28cm) gives the best result because when decreasing the height between the glass cover and absorbing plate, the area between them decreased and the design velocity increased then the efficiency of solar chimney model was increased.